The purpose of this project is to investigate the causes of cognitive deterioration in the elderly, using for the first time, reliable electrophysiological (EEG and AER) correlates of cognitive impairment in conjunction with psychometric, behavioral and pharmacological assessment techniques. In Part I, 200 geriatric out-patients, aged 60 and over, will receive extensive psychometric tests, psychiatric ratings and medical evaluations, as well as measurement of electrophysiological measures of cognitive impairment. Multivariate statistical procedures will be used to evaluate the validity of this assessment approach, and to gain information concerning the etiology of age-related cognitive decline. In Part II, pharmacological techniques will be used with the above assessment approach to further evaluate the electrophysiological measures, and to evaluate the hypothesis that reduction in neurotransmitter availability may be involved in the etiology of senility. Specifically, pharmacological agents will be administered to study the role of cholinergic and catecholamine neurotransmitters. A high, low and placebo dose of physostigmine will be given to 24 patients (drawn from the 200 patients in Part I) in a double-blind, cross-over design, to evaluate the effect of an acute increase of acetylcholine on impaired cognitive functioning. In a 13 week single-blind study, Deanol will be given chronically for 10 weeks to evaluate the effects of a long-term increase of acetylcholine. In each of these studies, psychometric tests, behavioral ratings, electrophysiological measures and medical monitoring will be used to evaluate the effects of the medication.